Green energy looks so good until you look closely. What a waste!
It looks like they are going to get the go ahead for the first tidal barrage on the Severn Estuary. Sounds like a good idea, the tides are predictable and happen every day. Hmm.. hold on.. the tide goes out, turns round, comes back in then turns round again and does the whole cycle again. So will we generate any power when the tide is turning? Answer is NO.
Just looking at the figures for the Swansea barrage you see this. Peak capacity of 320MW but an estimated output of 495GWh. If the plant was running at 100% you’d expect 2.8TWh. That is a capacity factor of 17%. Oh dear oh dear…
The fact is the station will generate for about 14 hours a day. That leaves 10 hours to be covered by…. solar? Not if its night time or overcast. Wind? Wind doesn’t always blow. So what do we do?
Are there any plans for storage of the power to give 24/7 output? Appears not! Certainly there are no storage methods that could cope with that sort of power for that long. Even the pump storage stations are only good for a couple of hours.
So what happens. Well you will have some 320MW of fossil fuel burning gas turbines sat in reserve. And as it is periodic you won’t really be able to use nice efficient closed cycle ones. You’ll have to use the less efficient open cycle turbines. Bugger!
The difference in efficient between open cycle and closed cycle of 34% vs 51% wipes out any carbon saving the barrage would make. Oops! Didn’t think that through did we?
Sad fact is that for every ‘renewable’ power source you almost always have to install an equal amount of standby generation capacity. Until we crack storage, and Elon Musk’s powerwall ISN’T going to do this, there is no such thing as low carbon non-nuclear electricity.